The Stribeck Curve and Lubrication Conditions of Metallic and Polymeric Materials

ABSTRACTThe present work discusses the selection of metallic and polymeric materials to be used as bearings in water lubricated condition. The study depends on using Stribeck curve to compare the friction performance of metallic materials (aluminium, bronze and steel) as well as polymeric materials (polyamide, polyethylene terephthalate, polymethyl methacrylate and polytetrafluoroethylene) in boundary, mixed and hydrodynamic regimes. Experiments were carried out to investigate the friction coefficient of the tested materials under variable loads and sliding velocity in water lubricated medium. It was found that, using Stribeck curve can provide specific information about friction coefficient of lubricating sliding in the boundary, mixed and hydrodynamic lubrication regimes. The lubricating conditions were controlled by controlling sliding velocity and load. Bronze and steel showed lower friction values than aluminum. Generally, values of friction coefficient were relatively high due the weak lubricating property of water. PTFE displayed the minimum friction coefficient (0.02). This result confirms the recommendation of PTFE as bearing material. The minimum friction values experienced by PA 6 and PETP were 0.083 and 0.07 respectively. Those polymers can be recommended to be used as bearing material in water lubricating medium. Usage of PMMA as bearing material should be avoided due to its high friction values.